Garlic is a fragrant herb with multiple health benefits, including antioxidant, anti-inflammatory, anti-microbial, and anti-obesity effects. This study aims to determine the ability of garlic to reduce blood glucose levels and inhibit complications of diabetes mellitus in various organs of streptozotocin-induced diabetic rats. A total of 24 rats were randomly divided into four groups. In group 1, rats were only given a standard diet without streptozotocin induction. Group 2 rats were given a standard diet and induced with streptozotocin 60 mg/kg BW. Groups 3 and 4 were induced with streptozotocin and given garlic extract at low (500 mg/kg BW) and high (750 mg/kg BW) doses for 20 days. At the end of the study, it was found that high doses of garlic extract significantly reduced blood glucose, urea, ALT, and AST levels but did not significantly reduce creatinine levels. Histopathological features of the pancreas showed an increase in the number and width of the islets of Langerhans at both doses. The liver improved in the portal tract but not the lobular area. High doses of the garlic treatment were also able to reduce the glomerular damage. Garlic extract at high doses effectively reduced blood glucose levels and inhibited complications in the pancreas, liver, and kidneys of diabetic rats.